1. Field of the Invention
The present invention relates to an optical semiconductor device such as a laser diode unit, a laser photoreceptor unit or an optical communication module and a method of fabricating the same, and more particularly, it relates to improvements for increasing positional accuracy of an optical axis and simplifying the fabrication.
2. Background of the Invention
FIG. 24 is a front sectional view showing a conventional laser diode unit 1. In this laser diode unit 1, a laser diode element 12 and a photoreceptor 13 are fixed to a side surface of a conductor block 17 which is fixed onto a conductor substrate 14. The laser diode element 12 and the photoreceptor 13 are stored in a cap 9 which is fixed onto the substrate 14. A window which is covered with a transparent cover glass member 10 is provided on an upper surface of the cap 9, so that a laser beam emitted from the laser diode element 12 is transmitted to the exterior through this window.
Further, the laser diode element 12 and the photoreceptor 13 are electrically connected to the substrate 14 through the block 14, while the same are electrically connected to electrodes 15 and 16 which are fixed to the substrate 14 through insulators 11c, by conductor wires 18 and 19 respectively. A current is externally supplied through the substrate 14 and the electrode 15, so that the laser diode element 12 emits a laser beam. This laser beam is monitored by the photoreceptor 13. Namely, the photoreceptor 13 generates an output current in response to the intensity of the laser beam, so that this output current is taken out to the exterior through the substrate 14 and the electrode 16.
The laser beam which passes through the cover glass member 10 to be radiated to the exterior is guided through a prescribed optical path which is provided in the exterior, and employed for reading or writing information from or in an optical disk, for example. Alternatively, the laser beam is guided to an optical fiber member for communication, to be employed for transmitting information.
An external control unit (not shown) is connected to the substrate 14 and the electrodes 15 and 16, for supplying the current to the laser diode element 12. The output current of the photoreceptor 13 is so monitored that the value of the current which is supplied to the laser diode element 12 is adjusted to maintain light emission intensity of the laser diode element 12 at a constant level. Still another electrode (not shown) is connected to the substrate 14, so that the external control unit is electrically coupled with the substrate 14 through this electrode.
The cap 9 is adapted to protect the elements which are stored in its interior. Further, hermetic seals 11a, 11b and 11c are provided on joints between respective members defining the container storing these elements, thereby airtightly maintaining the container. Further, inert gas such as argon gas or nitrogen gas is injected into the container. Thus, the elements are placed in an inert gas atmosphere which is sealed against the exterior, so that the laser diode element 12 which is particularly weak against adhesion of a conductive substance such as moisture is protected.
In the conventional laser diode unit 1, as hereinabove described, the hermetic seals 11a, 11b and 11c are provided on three portions including a portion for taking out the optical output, a final sealing part and a portion for taking out the electrodes. In the first place, therefore, the fabrication steps are complicated and hence the fabrication cost is increased. In addition, it is difficult to locate the laser diode element 12 on a prescribed position, in the second place.